Advertisement

Advertisement

BIG PHYSICS, BIG QUESTIONS –

Furry submarines embarrass Swedish navy

By Rob Edwards

WHEN is a sub not a sub? The answer, as an embarrassed Swedish navy has had to admit, is when it’s a mink or an otter. What the navy thought was the sinister sound of Soviet propellers was in fact the furious paddling of little legs.

A scientific commission set up by the government and chaired by the former director of the Swedish Engineering Science Academy, Hans Forsberg, concludes that most of the invading submarines reported by the navy were mythical. Of more than 6000 reports of “alien underwater activity” between 1981 and 1994, the commission found firm evidence for only six incidents.

In every other case the evidence, often based on sightings by the public, was unreliable. The navy claimed that one underwater noise, similar to the sound of frying eggs, was caused by bubbles from submarines. It was more likely to have been caused by the natural movement of water, says the commission.

On 40 occasions between 1992 and 1994, a network of microphones attached to buoys detected the sound of bubbles caused by a rotational movement in the water. The navy estimated the speed at up to 200 rpm, and assumed it must be submarine propellers.

But the navy was wrong, says the commission. According to its secretary; Ingvar Akesson, tests with swimming mink have shown that they can produce the same readings as propellers. “It is very puzzling, but they do,” he says. The navy has accepted that in some cases it may have confused the two sounds.